1. Field of the Invention
Kudzu (Pueraria lobata) is a perennial leguminous vine introduced from Japan that produces a large starchy tuber-like root system. Now infesting over 7 million acres of the southeastern United States, and spreading at a rate of 120,000 acres per year, this plant represents a serious threat to productivity in its growing region.
This invention relates to novel methods for the control of kudzu based upon the application of conidia of Myrothecium verrucaria in herbicidally effective amounts. These methods, due to their systemic nature, do in fact provide superior control of the weed as compared to known commercial alternatives.
2. Description of the Prior Art
Several methods are known in the art for using microorganisms to control weeds and other pest plants. As disclosed in U.S. Pat. No. 3,999,973 (Daniel et al.), the anthracnose fungus Colletotrichum gloeosporiodes has been used to control the weed northern jointvetch and another strain of the fungus has been used to control winged waterprimrose. Colletotrichum malvarum has been used to control prickly sida. These three pathogens have been combined to control all three target weeds at once. In other experimental work, the fungus Alternaria macrospora has been used to control spurred anoda (Anoda cristata) [H. L. Walker, Weed Science, Vol.29, pp.505-507, 1981].
Research activity involving M. verrucaria is noted on page 8 of the IBG News, Vol.4, No. 1, May 1995 issue. U.S. Pat. No. 4,390,360 (Walker), describes "Control of Sicklepod; Showy Crotaria and Coffee Senna With a Fungal Pathogen" using a specific host strain of the fungus Alternaria cassiae to produce typical weed lesions which kill or suppress the respective weeds. U.S. Pat. No. 4,419,120 (Walker), discloses "Control of Prickly Sida, Velvetleaf, and Spurred Anoda With Fungal Pathogens" using a specific host strain of the fungus Fusarium lateritium to kill or suppress the respective weeds. U.S. Pat. No. 4,715,881 (Andersen et al.), details "Control of Eastern Black Nightshade With a Fungal Pathogen" using a strain of Colletotrichum coccodes which is pathogenic towards eastern black nightshade (Solanium prycanthum). U.S. Pat. Nos. 4,718,935 and 4,767,441 (Walker et al.), describe a "Method for the Preparation of Mycoherbicide-Containing Pellets" characterized by alginate gel pellets containing living fungus capable of producing conidia when exposed to sufficient light and moisture. U.S. Pat. Nos. 4,724,147 and 4,818,530 (Marois et al.), detail the "Preparation of Pellets Containing Fungi for Control of Soilborne Diseases", in which fungi are first selected and grown for a time sufficient to produce inoculum. The fungal propagules are harvested, homogenized and diluted with sodium alginate solution. Pelletization is then accomplished by dropwise addition of the fungal propagule-alginate mixture into a solution of calcium chloride or calcium gluconate. The resulting alginate gel pellets containing living fungi can then be dried and used to inoculate agricultural fields infested with soilborne plant diseases. U.S. Pat. No. 5,192,541 (Savage et al.), describes "Weedkilling Xanthamonas campestris", in which novel microorganisms useful in controlling unwanted grasses and other weeds are discovered through a unique process which involves isolating plant pathogens from asymptomatic plants. U.S. Pat. No. 5,393,728 (Charudatten et al.), details a "Broad Spectrum Bioherbicide to Control Several Species of Pigweeds", in which a novel Phomopsis sp. fungus is used as an effective broad-spectrum bioherbicide for controlling pigweed.
U.S. Pat. No. 5,747,029 (Walker et al.), hereby incorporated by reference, teaches methods for the biological control of various weeds including sicklepod, pigweed, spurred anoda, jimsonweed, and hemp sesbania using the fungus M. verrucaria . This work, while showing that M. verrucaria is effective in controlling a number of varieties of weeds in several different types of important agricultural crops, shows that effective control of a given species is more the exception than the rule and that the host range for this fungus was not predictable (Col. 2, lines 66-67). Effective control, where it occurred, also required the presence of a dew period. The prior art as a whole teaches that fungi developed as biological herbicides should be restricted in host range to a limited number of plant species.